This section provides background information related to the present disclosure which is not necessarily prior art.
Exhaust after-treatment systems may dose an exhaust treatment fluid into the exhaust stream to assist in chemical reactions that remove NOx from the exhaust stream. The exhaust treatment fluid may be stored in a storage tank that communicates with a dosing module, which doses the exhaust treatment fluid into the exhaust stream. The storage tank may include various sensors for determining a temperature of the fluid level, a fluid level in the tank, and a concentration of the fluid in the tank. When the exhaust treatment fluid is a urea solution, the solution may freeze in cold temperatures. To prevent freezing of the urea solution in the dosing module, the dosing module may be purged and the unused urea solution may be returned to the tank. After being purged, the system generally must be primed before dosing of the urea solution can resume. During the priming process, the urea solution is cycled from the tank, through the dosing module, and back to the tank. The return of the urea solution to the tank may sometimes interfere with operation of the various sensors in the tank.